1) Field of the Invention
The present invention relates to a stent device and, in more particular, to a stent device that is capable of being positioned within a lumen.
2) Description of Related Art
Stents are devices that are inserted into body lumens such as vessels or passages to keep the lumen open and prevent closure due to a stricture, external compression, or internal obstruction. In particular, stents are commonly used to keep blood vessels open in the coronary arteries, and they are frequently inserted into the ureters to maintain drainage from the kidneys, the bile duct for pancreatic cancer or cholangiocarcinoma, or the esophagus for strictures or cancer. Vascular as well as nonvascular stenting has evolved significantly; unfortunately, there remain significant limitations with respect to the effectiveness of the stents following implantation into a patient's duodenum.
Stenting of the duodenum has proven to be challenging. The duodenum is a generally C-shaped portion of the small intestine that extends between the stomach and the jejunum. The duodenum is subject to complications that may require stenting, surgical repair, or balloon dilatation. For example, a defective portion of the duodenum such as a benign or malignant tumor is typically surgically removed, and the two cut ends are brought together and reattached. Months or years later a stricture may develop within the lumen of the duodenum either from the buildup of fibrous tissue proximate to the repaired lumen or from the growth of a malignant tumor, each necessitating stenting or further surgical repair to prevent the lumen from constricting further.
Conventional stents utilized for the duodenum have significant drawbacks. Because the duodenum is very soft and flexible compared to other lumens, preventing migration of the stent is problematic. In particular, the duodenum frequently changes size and position, which causes complications for typical stents. For instance, a stent having a constant diameter along its entire axial length will have a tendency to migrate as the duodenum expands. The stricture is narrower than the lumen located proximally and distally of the stricture, and the stent is longer than the length of the stricture such that the portion of the stent proximate to the stricture does not help prevent the stent from migrating. Therefore, there is an increased possibility that the stent will migrate or even turn sideways within the lumen. Moreover, the duodenum is very soft and flexible compared to other lumens, which presents design challenges. For example, the duodenum could fold over itself and slide into the openings of the stent, effectively occluding the stent.
Thus, there is a need in the industry for a duodenum stent that is capable of conforming to a lumen and maintaining the opening through a stricture. In addition, there is a need for a duodenum stent that reduces migration and the possibility of obstruction of the stent openings.